King Tide Floods in Tuvalu

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EGU Journal Logos (RGB) Open Access Open Access Open Access Advances in Annales Nonlinear Processes Geosciences Geophysicae in Geophysics icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion Open Access Open Access Nat. Hazards Earth Syst. Sci. Discuss.,Natural 1, 1943–1964, Hazards 2013 Natural Hazards www.nat-hazards-earth-syst-sci-discuss.net/1/1943/2013/ and Earth System doi:10.5194/nhessd-1-1943-2013and Earth System NHESSD Sciences Sciences © Author(s) 2013. CC Attribution 3.0 License. 1, 1943–1964, 2013 Discussions Open Access Open Access Atmospheric Atmospheric This discussion paper is/has been under review for the journal Natural Hazards and Earth Chemistry Chemistry King Tide floods in System Sciences (NHESS). Please refer to the corresponding final paper in NHESS if available. and Physics and Physics Tuvalu Discussions Open Access Open Access C.-C. Lin et al. Atmospheric Atmospheric Measurement Measurement Techniques Techniques Title Page Discussions Open Access King Tide floods in Tuvalu Open Access Abstract Introduction Biogeosciences C.-C. Lin, C.-R. Ho, andBiogeosciences Y.-H. Cheng Discussions Conclusions References Department of Marine Environmental Informatics, National Taiwan Ocean University, Open Access Open Access Tables Figures Keelung, Taiwan Climate Climate Received: 16 March 2013 – Accepted: 25 April 2013 – Published: 17 Mayof 2013 the Past of the Past J I Discussions Correspondence to: C.-R. Ho ([email protected]) J I Open Access Open Access Published by Copernicus Publications on behalf of the European GeosciencesEarth System Union. Earth System Back Close Dynamics Dynamics Discussions Full Screen / Esc Open Access Geoscientific Geoscientific Open Access Printer-friendly Version Instrumentation Instrumentation Methods and Methods and Interactive Discussion Data Systems Data Systems Discussions Open Access Open Access Geoscientific Geoscientific Model Development Model Development1943 Discussions Open Access Open Access Hydrology and Hydrology and Earth System Earth System Sciences Sciences Discussions Open Access Open Access Ocean Science Ocean Science Discussions Open Access Open Access Solid Earth Solid Earth Discussions Open Access Open Access

The Cryosphere The Cryosphere Discussions icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion Abstract NHESSD The spatial and temporal distributions of sea level rise present regional floods in some certain areas. The low-lying island countries are obviously the spots affected severely. 1, 1943–1964, 2013 Tuvalu, an atoll island country located in the south-west Pacific Ocean, is suffering the 5 devastating effects of losing life, property, and intending migration caused by floods. King Tide floods in They blame the regional flooding to King Tide, a term used but not clearly identified by Tuvalu Pacific islanders. In this study, we clarify what King Tide is first. By the tide gauge and topography data, we estimated the reasonable value of 3.2 m as the threshold of King C.-C. Lin et al. Tide. This definition also fits to the statement by National Oceanic and Atmospheric 10 Administration (NOAA) of King Tide occurring once or twice a year. In addition, We cross validate the 19 yr data of tide gauge and satellite altimeter (1993–2012), the Title Page

correlation coefficient indicates King Tide phenomenon is considerable connected to Abstract Introduction warm water mass. The 28 King Tide events revealed the fact that flooding can be referenced against spring tide levels, so can it be turned up by warm water mass. The Conclusions References 15 warm water mass pushes up sea level; once spring tide, storm surge, or other climate Tables Figures variability overlaps it, the rising sea level might overflow and so has been called “King Tide” for the floods in Tuvalu. This study provides more understanding of the signals of King Tide and an island country case study of regional sea level rise. J I

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1 Introduction Back Close

20 As with the impacts of global warming and climate change, inundation and flooding Full Screen / Esc have become the common threats to island countries in the tropical oceans (Mimura et al., 2007). Tuvalu with the highest point less than 5 m up to sea level, is broadly Printer-friendly Version considered to be one of the island country most threatened by sea level rise (Church et al., 2006; Mimura et al., 2007; Webb and Kench, 2010; Wong, 2011). Because of Interactive Discussion 25 the low-lying setting and the vulnerable characteristic of coral islands, any oceanic influential factors which were made worse by the effects of human and nature, can cause 1944 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion damages. The people in Tuvalu are already experiencing flooding in places. They call those floods pulling the Pacific Ocean farther ashore than normal “King Tide”, a term NHESSD connected to threaten their lives and properties. Not only wash over the coastline, it 1, 1943–1964, 2013 also seeps through small holes in the porous atoll ground which may wash away soils, 5 kill crops, contaminate freshwater, increase risk of disease, and decline agricultural productivity (Mortreux and Barnett, 2009). Originally, King Tide refers to any high tide King Tide floods in well above average height, or the highest spring tide in every year occurring in sum- Tuvalu mer or winter (http://www.msq.qld.gov.au/Tides/King-tides.aspx). The popular concept is that the King Tide is simply the very highest tide that usually occurs around the full C.-C. Lin et al. 10 moon or new moon. Back to the phenomenon of King Tide here, it is neither a high water phenomenon existing always, nor a series of continuous events, it happens mostly Title Page on the specific days of a year with regular tidal fluctuation. The duration can last for hours to days, but it leaves behind a trail of unforgettable disaster (EPA, 2011). There Abstract Introduction has been estimated the highest astronomical tide in Tuvalu should occur on 28 Febru- Conclusions References 15 ary 2006 over the period of 1990–2016 (AusAID, 2006). That day was as expected of

occurring King Tide, bringing the severest floods with the record of sea level 3.44 m. Tables Figures Though adjusted of barometric and harmonic analysis, there still has been 20 cm unknown residuals left (AusAID, 2007). We regarded the combination of astronomical tide J I and regional climate activities can mainly be explained to the inundation of Tuvalu, but 20 what cause the unknown residuals need to be explained. J I Sea level rise is normally the first impression connected to global warming. Of many Back Close things about global warming misunderstood by the public when sea level rise is mentioned, it typically refers to the global average, but this obscures the fact that not all Full Screen / Esc areas are rising. On the opposite, when we mentioned about flooding, it does not re- 25 fer to sea level rise globally. Limited by the length and accuracy of data, the historical Printer-friendly Version and projected sea level is always a subject of considerable and controversial in Tu- valu. Some previous studies (Becker et al., 2012; Cazenave and Llovel, 2010; Nerem Interactive Discussion et al., 2006) indicated that sea level in the western tropical Pacific is 3–4 times larger than the global average. A comment by Hunter (2002) noted a cautious estimate of

1945 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion present long-term sea level change at Tuvalu was a rate of rise between −1.1 and 2.7 mmyr−1 relative to the land, concerning the data affected by El Nino/Southern˜ Os- NHESSD cillation (ENSO) events. It’s of very similar magnitudes to the Intergovernmental Panel 1, 1943–1964, 2013 on Climate Change (IPCC) estimate of global average sea level rise during the 20th −1 5 century, 1–2 mmyr (Church et al., 2001). Eschenbach (2004a, b) estimated the rate of rise of 0.07 mmyr−1 based on an analysis of Mitchell et al. (2001) for the period King Tide floods in 1977–1998. Cabanes et al. (2001) used the sea level data from tide gauge for the Tuvalu period 1955–1996 but found out mean sea level has fallen in Tuvalu. Somehow, a con- sensus view unveils sea level rise is a trend and will be an unpreventable issue. The C.-C. Lin et al. 10 United States Environmental Protection Agency called the world that sea level rise will make today’s King Tides become the future’s everyday tides (EPA, 2011). The regional Title Page flooding or King Tide flooding will be more frequent and more severe. By the analysis of tide gauge and satellite altimeter data, Tuvalu’s present problem of inundation seems Abstract Introduction not simply being contributed by long trend of sea level rise by global warming. Some Conclusions References 15 oceanic factors need to be concerned.

Except for estimating the basic foundation of regional sea level, examining the mech- Tables Figures anisms of ocean can help to understand sea level variability precisely. The sea level in tropical Pacific variability has been regarded with the association of ENSO (Tren- J I berth and Hurrell, 1994; Chambers et al., 2002; Church et al., 2006), the Asian– 20 Australian monsoon or the Pacific Decadal Oscillation (PDO) (Mantua et al., 1997). J I Cabanes et al. (2001) revealed that the dominant contribution to regional sea level Back Close variability results from non-uniform changes in ocean thermal expansion. Cazenave and Llovel (2010) indicated about 30 % of the observed rate of rise during 1993–2007 Full Screen / Esc was caused by ocean thermal expansion. Houghton et al. (1996) estimated that half 25 of rising was due to steric heating. Merrifield (2011) pointed out the sea level trend in Printer-friendly Version the western tropical Pacific has linked to remote wind forcing. In tropical area of 10◦ N– 10◦ S, the trade wind drives currents westward along the equator, feeds and maintains Interactive Discussion the high water on the western side of the Pacific, which contributes to regional sea level rise a bit.

1946 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion Many factors and components are connected to the change of sea level, and some of the mechanisms of driving sea level have been analyzed. This study differs from NHESSD the usual attempts to determine how much sea level rises in Tuvalu or how many cen- 1, 1943–1964, 2013 timeters response driven by variable factors. We focus on the definition of King Tide, 5 the possible mechanisms intensify King Tide events, and the discussion of King Tide events during 1993–2012. First, a threshold of King Tide was identified to confine our King Tide floods in discussion of flooding events. Then we discussed the oceanic factors of King Tide Tuvalu events. We took tide gauge data and satellite altimeter data as basic data, removed the barometric pressure effect, used harmonic method to filter out the tidal influence, C.-C. Lin et al. 10 then the correlation coefficient and unknown residuals unveiled the true factors of regional flooding. By the snap shoot and discussion of King Tide, we sincerely hope Title Page offering a different view to understand the signals of King Tide and temporary regional sea level rise in tropical islands. Abstract Introduction

Conclusions References 2 Regional setting Tables Figures

15 Tuvalu, a Pacific island country, located in the south-west Pacific (Fig. 1) between 6 ◦ ◦ and 10 S latitude, and from 176 to 180 E longitude, comprising four reef islands and J I five atolls. Owning to the characteristic of coral atoll, the inland is at increased risk of flooding as well as the shoreline in Tuvalu. The central part of Fongafale is formed by J I extensive swampland and mangroves, sea water always oozes out of the ground, and Back Close 20 pond water can also go in and out through the lower part of the storm ridge during spring tide (Webb, 2006; Yamano et al., 2007). Once the extreme spring tide hits the Full Screen / Esc island, the water surges up from underground through the coral, the main road and nearby houses are also submerged. With the mean sea level elevation around 2 m, Printer-friendly Version the low-lying atoll island is vulnerable to any oceanic fluctuation. Referring to sea level Interactive Discussion 25 rise impact in Fongafale, the capital island of Tuvalu, nature and anthropogenic sides are supposed to be described. Morphologically, the island was eroded and reshaped. The historic combination of being a base of American army during World War II (WWII) 1947 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion strengthened the natural effects (Lewis, 1989; Eschenbach, 2004a). US army building a straight airport runway in Fongafale, and excavating a wide channel during WWII NHESSD broadened the erosion. On the other side, high population density of about 1600 per 1, 1943–1964, 2013 km2 (Secretariat of the Pacific Community, 2005), limited land resources of fresh wa- 5 ter and food, vulnerability to natural hazards, threatened biodiversity (Wong, 2011), all above made Tuvalu more vulnerable. The last shoot of psychological awareness King Tide floods in came on one response of Kyoto conference in 1997. The United States and Australia Tuvalu governments failed on promising CO2 emission reduction, which provoked Tuvaluans call the international of being the less contributors to global warming, but the first cli- C.-C. Lin et al. 10 mate refugees. So far, the spotlight of the global warming and Tuvalu seems connected tightly. Title Page

Abstract Introduction 3 Data sets and methods Conclusions References Sea level records show variability over a wide range of different time scales, includ- ing ranging from hours to years of tidal oscillations, hours to weeks of weather scale Tables Figures 15 phenomena, seasonal variation, interanual variations, or over periods of ten years to geological times scale. Estimates of regional short-term sea level variation are primarily J I based on the historical tide gauge data. The raw data from 1993 to 2012 are accessed from South Pacific Sea Level and Climate Monitoring Project (SPSLCMP) (http://www. J I bom.gov.au/oceanography/projects/spslcmp/spslcmp.shtml), sponsored by Australian Back Close 20 Agency for International Development (AusAID). The Sea Level Fine Resolution Acous- tic Measuring Equipment (SEAFRAME) gauge in Tuvalu was installed in 1993, offering Full Screen / Esc accurate data of sea level measurement, air and water temperatures, wind speed, wind direction and atmospheric pressure. All parameters are collected for 2 min record of ev- Printer-friendly Version ery 6 min and averaged to each hour. Sea level readings are taken every 3 min record Interactive Discussion 25 of each 6 min by calculating the traveling time of a sound pulse from and back between acoustic head and sea surface to one hour one datum. The sea surface height

1948 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion is revised by the assistance of Continuous Global Positioning System (CGPS) network and Tide Gauge Bench Mark (TGBM) for vertical movement. NHESSD Sea Surface Height (SSH) data are accessed from Archiving Validation and Inter- 1, 1943–1964, 2013 pretation of Satellite Data in Oceanography (AVISO). It is a merged product derived ◦ 5 from TOPEX/Poseidon, Jason-1/2, ERS-1/2, and ENVISAT satellites with a 1/4 spatial resolution and 7 day temporal intervals. The along track sea level data based on three King Tide floods in satellites (Topex/Poseidon, Jason-1, and Jason-2) is used to interpolate one datum Tuvalu each hour to match with tide gauge data. Cycle 173 of along track (Fig. 2), the nearest track to the tide gauge at Fongafale was used. There are about 714 points valid data C.-C. Lin et al. 10 matched up to the middle of 2012. Atmospheric pressure is one parameter potentially influencing local measurements Title Page of relative sea level rise. Variations in barometric pressure do not cause changes in global ocean volume, but they affect sea level to rise or fall by the shifting weather pat- Abstract Introduction terns. A 1 hPa decrease sustained over a day could cause a 1 cm increase in relative −1 Conclusions References 15 sea level (AusAID, 2010), or an inverted barometer response of 0.995 cmmbar de-

crease (increase) in atmospheric pressure (Fu and Pihos, 1994). The inverted barome- Tables Figures ter response was calculated as Eq. (1) mentioned by Jeffreys (1916). η(t) is the oceanic 0 sea level change; pa(t) is an atmospheric pressure change measured in millibars; while −3 J I g is the gravitational acceleration and ρ0 indicates the water density (∼ 1.02 gcm ) J I 0 pa(t) 20 η(t) = − . (1) Back Close ρ0g Full Screen / Esc After barometric influence removed, we took harmonic analysis as the method to calculate the amplitudes and phases of tidal characteristics. The tidal signal, modeled Printer-friendly Version as the sum of a finite set of sinusoids at specific frequencies, was related to astronomical parameters. These frequencies are specified by various combinations of sums Interactive Discussion 25 and differences of 6 fundamental frequencies arising from planetary motions (Godin, 1972), which includes the rotation of the earth, the orbit of the moon around the earth, the earth around the sun, the lunar perigee, the lunar orbital tilt, and the perihelion 1949 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion (Pawlowicz et al., 2002). Harmonic analysis displayed the tidal constituents of 186 constituents, with 95 % confidence interval. NHESSD 1, 1943–1964, 2013 4 Results King Tide floods in King Tide, a layman’s term in Pacific, has been identified by United States of Environ- Tuvalu 5 mental Protection Agency (EPA, 2011) as the highest predicted high tide of the year at a coastal location. The Queensland Government of Australia (http://www.msq.qld. C.-C. Lin et al. gov.au/Tides/King-tides.aspx) takes any high tide well above average height, or the higher high waters which occur around Christmas time as King Tide. Green Cross (http://www.witnesskingtides.org/what-are-king-tides.aspx) regards it as an especially Title Page 10 high tide event occurring twice a year, similar to the definition as National Oceanic and Atmospheric Administration (NOAA) of a normal occurrence once or twice a year. Abstract Introduction

Therefore, King Tide is clearly explained to the gravitational forces exerted by the Moon Conclusions References and the Sun and the rotation of the Earth. All above indicate the significant relation of highest tide and King Tide. If gravitational force can simplify the happening of King Tide, Tables Figures 15 the highest astronomical tide (HAT) of every year should occur the severest floods in every year. But the fact displayed sea surface height (SSH) in the highest astronomical J I tide of 1998 had 38 cm fall than expected; and same to the case in 2010 of 23 cm fall. King Tide definition cannot be simplified to the highest predicted high tide only, there J I must have some other conditions need to be concerned. In this study, the previous Back Close 20 studies and the tide gauge data which reflects regional sea level, the real flooding sit- uation, and the pains people suffering are taken to estimate a reasonable threshold of Full Screen / Esc the King Tide. Generally, mean lower low water (MLLW) is the average height of the lowest tide Printer-friendly Version recorded at a tide station during the recording period. The line on a chart represents the Interactive Discussion 25 intersection of the land with the water surface at the elevation of mean lower low water. In Fongafale, the 19 yr (1993–2012) MLLW was 1.37 m relative to the chart datum, which is the lowest expected tidal level at a particular location and can be considered as 1950 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion the level relative to the depths on nautical charts and tidal levels. The average altitude of Tuvalu was reported 1.83 m (United Nations, 2008) relative to MLLW. The addition NHESSD of both comes to the value of 3.2 m which we assumed to be a reasonable threshold 1, 1943–1964, 2013 of King Tide. Under the definition, once sea level measures over 3.2 m, we definitely 5 consider sea water rises up to the average height of Fongafale land, half of the island land could be flooded by sea water. During the record years of tide gauge station King Tide floods in set, there are 108 records of one datum each hour over than 3.2 m. The continuous Tuvalu records at the same spring tide are generalized to one King Tide event, therefore, the total amount brings about 28 events. The average amount of each year comes to 1.5 C.-C. Lin et al. 10 events, which satisfies with the introduction by Tuvaluans, also fits with the identification by NOAA: a normal occurrence once or twice every year in coastal areas. Title Page The total amount of 28 King Tide events are shown in Table 1. Every King Tide event happened during spring tide period, but less than half of them occurred at the HAT Abstract Introduction period. The events happened in 1993–1995, 1998–2000, 2003–2005, 2008, 2010, and Conclusions References 15 2012 are out of HAT period. NOAA defined King Tide as the highest predicted high tide

of the year; however, the fact of King Tide events in Tuvalu seems not accommodated. Tables Figures Although the gravitational force contributes sea level, without the other factors involved, the King Tide threshold will not be achieved. HAT is one optional component of King J I Tide, not essential. 20 Besides, Queensland Government deﬁnes King Tide as any high tide well above J I average height, or the higher high waters which occur around Christmas time. This Back Close identiﬁcation cannot be imitated by Tuvalu of the fact that the higher high tide average is 2.7 m. If it is taken as the threshold of King Tide, then King Tide is every month tide. Full Screen / Esc On the other side, 90 % of King Tide events happened on the month of January–March. 25 From the point of the gravitational force, the theory of celestial cycle is acceptable. Printer-friendly Version The perihelion, the point earth comes closest to the sun, is on 2 January at present. In order to expose the unknown residuals of sea level rise, we examined and com- Interactive Discussion pared the data of tide gauge and satellite altimeter. The root-mean-square error of both data reaches a value of 4.37 cm (Fig. 3) which meets the uncertainty of satellite

1951 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion altimeter data (Dibarboure et al., 2011). Interest in the King Tide phenomenon has been strengthened with the recognition of warm water mass, which is described as the NHESSD motion of water within the ocean driven by the Rossby waves or the equatorial current. 1, 1943–1964, 2013 Maps of sea surace height anomaly (SSHA) with data derived from satellite altimetry 5 demonstrated that Tuvalu is surrounded by the warm water mass most of the flooding time. Figure 4 shows the fact that King Tide events are accompanied with warm water King Tide floods in masses. The anomaly high water is diagramed by red colour, passing through from Tuvalu east to west. Once the warm water mass passing Tuvalu runs into the spring tide, SSH turns out an effective action. The impact of warm water mass brings 26 cm maximum C.-C. Lin et al. 10 of SSH for the King Tide events. Except the event occurred in 2010, all the others happened with warm water masses company, and pushed up SSH a 17 cm in average. Title Page The King Tide events occurred on 1 February 1999, 9 March 2001, and 17 April 2007 (Fig. 4) were not occurring in the HAT period of that year; but warm water masses Abstract Introduction made SSHA rise 21, 25, and 23 cm, respectively. The latter condition piled up the sea Conclusions References 15 level high enough to be concerned with King Tide.

Tables Figures 5 Discussion J I As the display of Table 1 shows, the duration of King Tide (1–5 days) matches well with tidal period. Definitely, gravitation of moon pulling up sea level is one of the most J I important factors. Every King Tide event happening on full moon or new moon period Back Close 20 clearly demonstrates that tidal fluctuation is the very first basic foundation of flooding. Warm water mass brought by the oceanic dynamic piling up the sea water is also one Full Screen / Esc significant factor cannot be ignored. The duration of warm water mass formation, pass, and diminishing will be the future study to predict the duration of flooding. For the detail Printer-friendly Version understanding of King Tide events, we discuss the influential impacts depending on Interactive Discussion 25 the time and the amplitude of running into the spring tide. Some other components as below which are last but not least factors, need to be considered further.

1952 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion Regarding to the impact of El Nino˜ and La Nin˜ a events, Tuvalu located in the tropical Pacific, is definitely affected by the interannual sea surface temperature and barometric NHESSD pressure variations. Since we had filtered out the influence of barometric in data pro- 1, 1943–1964, 2013 cessing, the ENSO effect should be out of discussion here. But taking a quick view of El 5 Nino,˜ sea level is anomalously high in the eastern tropical Pacific and low in the western tropical Pacific. The easterly surface wind, that usually extending all the way across King Tide floods in the equatorial Pacific, begins to weaken, sea water flows back to the east Pacific. Si- Tuvalu multaneously, it drops down in the western Pacific where Tuvalu locates. As we check the King Tide events list out in Table 1, no King Tide record showed in 1998. Maps of C.-C. Lin et al. 10 SSHA indicating the cold water feature instead. On the contrary, Tuvalu experienced floods in La Nina˜ periods than usual. Title Page Referring to tropical cyclones effects, Tuvalu, situated in latitude 5.3–11◦ S, a site pro- duces tropical cyclones instead of being attacked. Since the installation of SEAFRAME Abstract Introduction tide gauge in 1993, tropical Cyclone Gavin was the only one detected Tuvalu. The storm Conclusions References 15 surge did not make King Tide event due to no support of spring time, though reached

a peak of 0.3 m by the surge. Tables Figures As for the short term effects of tsunami, there were 17 separate tsunami events detected since its installation. The highest surge record was 10 cm caused by the earth- J I quake of magnitude Mw = 8.8 that occurred of Chile on 27 February 2010 (AusAID, 20 2010). SSHA (Fig. 5a) unveils of fact of time that Tuvalu was surrounded by cold wa- J I ter. The energy of ocean dynamic cuts down the SSH foundation and diminished the Back Close effects of tsunami. Instead of sea level rising, a fall of 10–20 cm was recorded at that time. But the other earthquake of magnitude Mw = 8.2 near Irian Jaya happened on 17 Full Screen / Esc February 1996 (Fig. 5b) was not as lucky as the last one. The occurrence on spring 25 tide with warm water mass, and the slight effects of La Nina˜ contributed to the flooding Printer-friendly Version of King Tide event. Interactive Discussion

1953 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion 6 Conclusions NHESSD As with sea level rise, the state of an individual flooding happened on a given day or a given place is not proof of global trend, but regional sea level variation implying 1, 1943–1964, 2013 sea level fluctuation is obviously complicated. Regional sea level change may be re- 5 acted by many factors, such as: isostatic rebound; climate variability (Merrifield, 2011; King Tide floods in Timmermann et al., 2010); interannual influence; non-uniform changes in ocean ther- Tuvalu mal expansion (Cabanes et al., 2001; Cazenave and Nerem, 2004); or the warm water mass. Nevertheless, not all above will play key roles in the low-lying island countries; C.-C. Lin et al. neither can they be well predicted or prevented by local government. In this study, 10 a definition of King Tide is recommended to be introduced and applied in Tuvalu area, a reasonable threshold to examine the floods inducing by King Tide, which could satisfy Title Page

the needs of local people. We make the term King Tide proper to the fact of occurring Abstract Introduction once or twice a year; also can it represent the Tuvaluans’ deeper fear of losing their land and life. The results indicate the straight relationship of King Tide and the possible Conclusions References 15 mechanisms raising sea level. The warm water mass, one of the key factors but easily Tables Figures be ignored, arises the SSH should not be underestimated. Some of the potential King Tides, occurring with the contributions of warm water mass but in low tide period of SSH under the threshold, are not included in this research. J I

Acknowledgements. The tide gage and satellite altimeter data are accessed from SPSLCMP J I 20 and AVISO, respectively. This work was partly supported by the National Science Council of Back Close Taiwan through grant NSC101-2611-M-019-003. Full Screen / Esc

References Printer-friendly Version

AusAID: Paciﬁc country report on sea level and climate: their present state, Australian Agency Interactive Discussion for International Development, Tuvalu, 2006. 25 AusAID: Paciﬁc country report on sea level and climate: their present state, Australian Agency for International Development, Tuvalu, 2007.

1954 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion AusAID: Pacific country report on sea level and climate: their present state, Australian Agency for International Development, Tuvalu, 2010. NHESSD Becker, M., Meyssignac, B., Letetrel, C., Llovel, W., Cazenave, A., and Delcroix, T.: Sea level variations at tropical Pacific islands since 1950, Global Planet. Change, 80–81, 85–98, 1, 1943–1964, 2013 5 doi:10.1016/j.gloplacha.2011.09.004, 2012. Cabanes, C., Cazenave, A., and Le Provost, C.: Sea level rise during past 40 years determined from satellite and in situ observations, Science, 294, 840–842, King Tide floods in doi:10.1126/science.1063556, 2001. Tuvalu Cazenave, A. and Llovel, W.: Contemporary sea level rise, Annu. Rev. Mar. Sci., 2, 145–173, C.-C. Lin et al. 10 doi:10.1146/annurev-marine-120308-081105, 2010. Cazenave, A. and Nerem, R. S.: Present-day sea level change: observations and causes, J. Geophys. Res., 42, RG3001, doi:10.1029/2003RG000139, 2004. Chambers, D. P., Melhaff, C. A., Urban, T. J., Fuji, D., and Nerem, R. S.: Low- Title Page frequency variations in global mean sea level: 1950–2000, J. Geophys. Res., 107, 1–10, 15 doi:10.1029/2001JC001089, 2002. Abstract Introduction Church, J. A., Gregory, J. M., Huybrechts, P., Kuhn, M., Lambeck, K., Nhuan, M. T., Qin, D., and Woodworth, P. L.: Changes in sea level, in: Climate Change 2001: The Scientific Basis, Conclusions References Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Tables Figures Panel on Climate Change, edited by: Houghton, J. T., Ding, Y., Griggs, D. J., Noguer, M., 20 van der Linden, P. J., Dai, X., Maskell, K., and Johnson, C. A., Cambridge University Press, Cambridge, UK and NY, USA, 639–693, 2001. J I Church, J. A., White, N. J., and Hunter, J. R.: Sea level rise at tropical Pacific and Indian Ocean islands, Global Planet. Change, 53, 155–168, doi:10.1016/j.gloplacha.2006.04.001, 2006. J I Dibarboure, G., Pujol, M.-I., Briol, F., Le Traon, P. Y., Larnicol, G., Picot, N., Mertz, F., and Back Close 25 Ablain, M.: Jason-2 in DUACS: updated system description, first tandem results and impact on processing and products, Mar. Geod., 34, 214–241, doi:10.1080/01490419.2011.584826, Full Screen / Esc 2011. EPA (United States of Environmental Protection Agency): King Tides Facts Sheet, EPA-842-F- Printer-friendly Version 11-010, available at: http://water.epa.gov/type/oceb/cre/upload/king tides factsheet.pdf, last 30 access: 1 February 2013, 2011. Interactive Discussion Eschenbach, W.: Tuvalu not experiencing increased sea level rise, Energy & Environment, 15, 527–543, 2004a.

1955 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion Eschenbach, W.: Response to John Hunter’s review, Energy & Environment, 15, 931–935, 2004b. NHESSD Fu, L. L. and Pihos, G.: Determining the response of sea level to atmospheric pressure forcing using TOPEX/POSEIDON data, J. Geophys. Res., 99, 24633–24642, 1, 1943–1964, 2013 5 doi:10.1029/94JC01647, 1994. Godin, G.: The Analysis of Tides, University of Toronto Press, Toronto, 285 pp., 1972. Houghton, J. T., MeiraFilho, L. G., Callander, B. A., Harris, N., Kattenberg, A., and Maskell, K.: King Tide floods in Climate Change 1995: The Science of Climate Change, Contribution of Working Group I to Tuvalu the Second Assessment Report of the Intergovernmental Panel on Climate Change, Cam- C.-C. Lin et al. 10 bridge University Press, Cambridge, 572 pp., 1996. Hunter, J. R.: A note on relative sea level change at Funafuti, Tuvalu, Antarctic Cooperative Research Center, Hobart, Australia, 2002. Jeffreys, H.: Causes contributory to the annual variation in latitude, Mon. Not. R. Astron. Soc., Title Page 76, 499–525, 1916. 15 Lewis, J.: Sea level rise: some implications for Tuvalu, Environmentalist, 9, 269–275, Abstract Introduction doi:10.1007/BF02241827, 1989. Mantua, N. J., Hare, S. R., Zhang, Y., Wallace, J. M., and Francis, R. C.: A Pacific interdecadal Conclusions References climate oscillation with impacts on salmon production, B. Am. Meteorol. Soc., 78, 1069–1079, Tables Figures doi:10.1175/1520-0477(1997)078<1069:APICOW>2.0.CO;2, 1997. 20 Merrifield, M. A.: A shift in western tropical Pacific sea level trends during the 1990s, J. Climate, 24, 4126–4138, doi:10.1175/2011JCLI3932.1, 2011. J I Mimura, N., Nurse, L., McLean, R., Agard, J., Briguglio, L., Lefale, P., Payet, R., and Sem, G.: Small islands, in: Climate Change 2007: Impacts, Adaptation and Vulnerability, Contribution J I of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Back Close 25 Climate Change, edited by: Parry, M., Canziani, O., Palutikof, J., van der Linden, P., and Hanson, C., Cambridge University Press, Cambridge, 687–716, 2007. Full Screen / Esc Mitchell, W., Chittleborough, J., Ronai, B., and Lennon, G. W.: Sea Level Rise in Australia and the Pacific, The South Pacific Sea Level and Climate Change Newsletter, Q. Newsl., 5, 10– Printer-friendly Version 19, 2000. 30 Mortreux, C. and Barnett, J.: Climate change, migration, and adaptation in Funafuti, Tuvalu, Interactive Discussion Global Environ. Change, 19, 105–112, 2009. Nerem, R., Leuliette, E., and Cazenave, A.: Present-day sea level change: a review, C. R. Geosci., 338, 1077–1083, doi:10.1016/j.crte.2006.09.001, 2006. 1956 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion Pawlowicz, R., Beardsley, R., and Lentz, S.: Classical tidal harmonic analysis include error estimates in MATLAB using T TIDE, Comput. Geosci., 28, 929–937, doi:10.1016/S0098- NHESSD 3004(02)00013-4, 2002. Queensland Government, Maritime Safety Queensland: available at: http://www.msq.qld.gov. 1, 1943–1964, 2013 5 au/Tides/King-tides.aspx/, last access: 1 February 2013. Secretariat of the Pacific Community: Tuvalu 2002 Population and Housing Census: Volume 1, Analytical Report, Secretariat of the Pacific Community, Noumea,´ 2005. King Tide floods in Trenberth, K. E. and Hurrell, J. W.: Decadal atmosphere-ocean variations in the Pacific, Clim. Tuvalu Dynam., 9, 303–319, 1994. C.-C. Lin et al. 10 Timmermann, A., McGregor, S., and Jin, F. F.: Wind effects on past and future regional sea level trends in the southern Indo-Pacific, J. Clim. Change, 23, 4429–4437, doi:10.1175/2010JCLI3519.1, 2010. United Nations: Effects of Climate Change on Indigenous Peoples: a Pacific Presentation, avail- Title Page able at: http://www.un.org/esa/socdev/unpfii/documents/EGM cs08 Elisara.doc, last access: 15 1 February 2013. Abstract Introduction Webb, A.: Tuvalu technical report – coastal change analysis using multi-temporal image com- parisons – Funafuti Atoll, EU EDF 8, SOPAC Project Report 54, 2006. Conclusions References Webb, A. P. and Kench, P. S.: The dynamic response of reef islands to sea level rise: evidence Tables Figures from multi-decadal analysis of island change in the Central Pacific, Global Planet. Change, 20 72, 234–246, doi:10.1016/j.gloplacha.2010.05.003, 2010. Wong, P. P.: Small island developing states, WIREs Clim Change, 2, 1–6, doi:10.1002/wcc.84, J I 2011. Yamano, H., Kayanne, H., Yamaguchi, T., Kuwahara, Y., Yokoki, H., Shimazaki, H., and J I Chikamori, M.: Atoll island vulnerability to flooding and inundation revealed by historical re- Back Close 25 construction: Fongafale Islet, Funafuti Atoll, Tuvalu, Global Planet. Change, 57, 407–416, doi:10.1016/j.gloplacha.2007.02.007, 2007. Full Screen / Esc

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Table 1. A check list of possible influential factors of 28 King Tide events. NHESSD 1, 1943–1964, 2013 Event Date Sea level Duration HAT Spring Warm Tsunami Tropical (m) (days) tide water mass cycle 1 26 Feb 1994 3.241 2 × + + × × King Tide floods in 2 21 Jan 1996 3.255 3 + + + × × Tuvalu 3 18 Feb 1996 3.312 4 × + + + × 4 18 Mar 1996 3.200 1 × + + × × C.-C. Lin et al. 5 8 Feb 1997 3.255 2 + + + × × 6 9 Mar 1997 3.304 4 × + + × × 7 1 Feb 1999 3.207 1 × + + × × 8 21 Jan 2000 3.236 2 × + + × × Title Page 9 9 Feb 2001 3.322 4 + + + × × 10 9 Mar 2001 3.347 4 × + + × × Abstract Introduction 11 30 Jan 2002 3.226 1 × + + × × 12 28 Feb 2002 3.309 3 + + + × × Conclusions References 13 28 Mar 2002 3.303 3 × + + × × 14 16 Apr 2003 3.253 2 × + + × × Tables Figures 15 15 May 2003 3.246 3 × + + × × 16 30 Jan 2006 3.358 4 × + + × × 17 28 Feb 2006 3.415 5 + + + × × J I 18 29 Mar 2006 3.236 2 × + + × × 19 18 Mar 2007 3.241 2 + + + × × J I 20 17 Apr 2007 3.262 3 × + + × × Back Close 21 22 Jan 2008 3.218 1 × + + × × 22 12 Jan 2009 3.234 2 × + + × × Full Screen / Esc 23 10 Feb 2009 3.271 2 + + + × × 24 30 Jan 2010 3.210 1 × + × × × 25 20 Jan 2011 3.286 3 × + + × × Printer-friendly Version 26 19 Feb 2011 3.223 2 + + + × × 27 20 Mar 2011 3.206 2 × + + × × Interactive Discussion 28 9 Mar 2012 3.200 2 × + + × × Note: + means the positive influence; × means non-influence.

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Full Screen / Esc Fig. 1. Location of Tuvalu and the relative position of Australia (left map). The upper right map is the relative position of Tuvalu nine atolls, Funafuti atoll is the main atoll of Tuvalu. And Fongafale Printer-friendly Version (bottom of right corner), the capital of Tuvalu referred to in the text, is shown by red triangle. Interactive Discussion

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Fig. 3. The root-mean-square error of tide gauge and altimeter data for 19 yr (March 1993– November 2012) reaches a value of 4.37 cm. Printer-friendly Version

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Fig. 4. Maps of SSHA during King Tide events. Star indicates the position of Tuvalu. The colour Printer-friendly Version bar shows the SSHA by cm. Red colour presents the warm water mass; while blue presents Interactive Discussion the cold water mass. The image is a 7 day average datum. The date indicated on the image is the middle date of the 7 days.

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Fig. 4. Continued. Interactive Discussion

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J I Fig. 5. (a) SSHA in the week of 24 Feb 2010 indicated that Tuvalu was under the background of cold water when surge caused by Chile earthquake occurred on 27 February 2010. No King J I Tide occurred at this moment. (b) SSHA in the week of 14 February 1996 presented the King Back Close Tide event response by the combination of spring tide, warm water mass, and tsunami surge on 17 February 1996. The date indicated on the image is the middle date of the 7 days. Full Screen / Esc

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